This is a great site. Thanks for compiling this. I've been an avid collector of the DCUs for years. It looks like I have a few new ones to add to the list:
Aquaman 4
Superman: The Man of Steel 50
And Flash #94 "stickered" (for the secondary list, maybe not the master list)
The Flash 94 is hard to see from this picture, but you may be able to tell that the DCU logo is not in the box. On the comic itself, I can clearly see a barcode behind the sticker (too hard to see if it's the direct or newsstand code).
Now, I have a question about the master list. Where did that come from? Specifically, was there photographic evidence of comics before they got added? A post a few days ago asked about Batman Adventures 18. As that post indicated, there is a bat symbol edition. I've never seen a DCU edition, though. With #17, there is a DCU edition but I've never seen a bat symbol edition. I think each of #14 - 30 has a bat symbol edition or a DCU edition -- but I've not seen one with both. So with 18, there is definitely the direct market, the newsstand and the bat symbol editions. A DCU edition would make a fourth version.
Likewise, I question Animaniacs 16. There is an edition that was in a 2-pack. The "flipside" was a DCU (Pinky & the Brain 1 DCU I think -- but I could be wrong on that). But the Animaniacs 16 had the Warner Brothers "READING" logo. So if there is a DCU of Animaniacs 16, then there are four different editions -- the direct market, the newsstand, the WB logo and the DCU. Like with the Batman Adventures 18, I've only seen evidence of one "special" edition -- not both.
Lastly, I question Adventures of Superman 530. Between this master list and the ones I have, there are about 525 reported DCUs. I spent time looking at the cover dates. Right now, AoS 530 is the only DCU listed with a December 1995 cover date. That seems suspicious. Of course, I say that but there is also October 1994 where there is only 1 (Damage 0). The others that month were the Zero Hour editions. So it's very possible that there is an AoS 530 that was the lone 12/95 cover date book in some random 2-pack. But I think it's also possible that, for whatever reason, DC skipped that month.
So, as a quick summary, the list is missing is Aquaman 4 and Superman: MoS 50. And, it seems that the stickered editions were being compiled as a secondary list, so there's also Flash 94.
And, I'm really skeptical about Batman Adventures 18, Animanics 16 and AoS 530 and would love to know how/why those were thought to exist.